| 摘要 |
PURPOSE:To discriminate the opening and closing state of a door pane or a window pane, by transmitting an ultrasonic wave with a transmitter comprising an ultrasonic vibrator into a vehicle, a dwelling room or the like. CONSTITUTION:The ultrasonic wave transmitted into a space area in a dwelling room, a vehicle or the like with a transmitter 1 normally has components of thermal noises of amplification circuits 5 and 8 or the like appearing at the output of the amplification circuit 8 when a window glass or the like is closed. But when the window pane or the like is opened, a Doppler component is generated due to the movement and the oscillation of air and when the Doppler component is received with a receiver 4, it is amplified to create saturation. Thus, comparing outputs of a detector 7 with a comparator 9 enables the detection of opening or closing stage of the window pane or the like. Depending on the output of the comparator 9, an output driving circuit 10 generates a signal when the window pane is opened or closed to drive a display or the like. |
